1. Field of the Invention
The present invention is directed in general to systems for operating railroad car hopper doors, and, in particular, to a system which selectively opens the doors on railroad hopper car doors.
2. Description of the Related Art
A common type of railroad freight car in use today is the freight car of the type wherein the load is discharged through hoppers in the underside of the body. Such cars are generally referred to as hopper cars and are used to haul coal, phosphate and other commodities.
After hopper cars are spotted over an unloading pit, the doors of the hoppers are opened, allowing the material within the hopper to be emptied into the pit.
Hopper cars, which may be covered, are usually found with one of two hopper configurations: transverse, in which the doors closing the hoppers are oriented perpendicular to the center line of the car; or longitudinal, in which the doors closing the hoppers are oriented parallel to the center line of the car. An example of a hopper car with transverse doors is shown in U.S. Pat. No. 5,249,531, while an example of a hopper car with longitudinal doors is shown in U.S. Pat. No. 4,224,877.
Prior art references which teach operating mechanisms for opening and closing hopper doors include U.S. Pat. Nos. 3,596,609; 4,741,274; 3,187,684; 3,611,947; 3,786,764; 3,815,514; 3,818,842; 3,949,681; 4,222,334; 4,366,757; 4,601,244; 5,823,118; and 5,249,531. There are several disadvantages to the hopper door operating mechanisms described in some of the aforementioned patents. One problem is that some of the prior art mechanisms are designed such that each actuating mechanism is connected to doors from two separate hoppers. Thus, if the mechanism fails, it effects the operation of two hoppers. Another disadvantage of some of the above described hopper door mechanisms is that the operating mechanisms limit the distance of the door motion, thus limiting the open area of the car's bottom. This arrangement slows the unloading process and causes additional costs and potential damage to the car due to increased periods in thaw sheds.
Finally, it is often desirable to empty the contents of a railcar while the car is in motion, thus allowing the car to be emptied quicker. Sometimes this is not possible when all of the hopper doors open simultaneously. It is necessary that the doors open in a sequential manner to allow dumping in motion.